The effectiveness of a detergent-bleach composition depends upon several factors including temperature of the washing solution, the nature of the soil being removed, the nature and concentration of the active cleaner, nature and concentration of the bleach, hardness of the water and the like. One important factor, in maintaining an effective concentration of bleach, is the stability of the bleach in the detergent-bleach composition. An active-halogen bleach can react with other components in a detergent-bleach composition resulting in a substantial loss of active-halogen bleach and a corresponding loss of other reactant.
Many encapsulating procedures known in the art suggest coating a particle of bleach to isolate it from other reactive components so that it may be usefully employed in a detergent composition. However, many of these encapsulated bleaches are not stable in highly alkaline environments. Further, the suggested encapsulating compounds such as tetrapotassium phosphate, hydratable inorganic salts and C.sub.12-22 fatty acids must be dissolved in the wash water to release the core of active halogen. As a result, the encapsulating compounds generally remain in the wash water and can interfere in either the washing or bleaching process. Further, the suggested encapsulating compounds do not act as an active detersive ingredient but are merely present to encapsulate the active-halogen bleach, thereby increasing the cost and decreasing the percentage of active components. An encapsulating compound which also acts as an active cleansing component would eliminate the introduction of unnecessary and unwanted compounds into the washing solution, reduce the cost of the detergent-bleach composition and increase the percentage of active components in the detergent bleach composition.
Encapsulation of an active-halogen source with a single inorganic coating is known in the art. Several examples of such compositions is disclosed in Brubaker, U.S. Pat. No. 4,279,764, Brennan, U.S. Pat. No. 3,637,509, Idudson, U.S. Pat. No. 3,650,961, and Alterman, U.S. Pat. Nos. 3,983,254 and 3,908,045. Brubaker discloses a bleaching composition comprising a chlorine bleach coated with a silicate bound, hydrated, soluble salt having an N--H chlorine accepting component. Brubaker discloses that the composition is useful in preventing dye and fabric damage caused by bleach particles during machine washing of fabrics. Brennan discloses the encapsulation of a mixture of an organic chlorinating agent and an alkali metal tripolyphosphate with tetrapotassium phosphate. Brennan discloses that the composition provides improved chlorine stability. Hudson discloses fluidized bed encapsulation with a hydratable inorganic salt. Hudson discloses that the core is a bleach the capsule provides improved bleach stability in detergent compositions. The Alterman patents disclose encapsulation with a C.sub.12-22 fatty acid and, when the core is a chlorine releasing agent, further encapsulation with a second coat of an alkali hydroxide. Alterman discloses that the capsule is effective in preventing bleach from causing pinholes in washed fabrics.
Accordingly, a substantial need exists for an oxidizing halogen bleach that is stable in a highly alkaline environment, does not substantially degrade other cleaning components, and does not introduce unwanted and unnecessary components into the wash water. Further, a substantial need exists for a highly alkaline storage stable detergent-bleach composition having substantially no degradation of the bleach contained therein.